Robotic assemblies, such as robotic arms, are commonly used in a variety of industrial applications. Among other things, robotic arms may be used to perform automated and repetitive functions, such as measuring, manufacturing, positioning, assembling parts, and the like, which may otherwise be cumbersome or more difficult to accomplish manually by hand. Such automated processes not only reduce the amount of tooling involved and the potential for human error, but also increase overall productivity and allow greater flexibility for the task performed. In aircraft manufacturing applications, for instance, robotic arms may be preprogrammed with algorithms and data that are not only capable of automating the installation of a variety of different aircraft components, but also easily reconfigurable to accommodate for case-specific changes in the automated process.
Robotic arms are often configured with a working end that can be fitted with a variety of interchangeable end-effectors or tools designed for different tasks. More particularly, the working end can be provided with a universal connector which uses releasable mechanical or pneumatic mechanisms to couple to different types of end-effectors. Furthermore, robotic arms may be preprogrammed to autonomously interchange between different end-effectors that may be available on one or more tool racks within reach of the robotic arm and readily attachable to the working end of the robotic arm. However, in order to enable a robotic arm to autonomously interchange between different end-effectors, the robotic arm may first need to be taught where the different end-effectors are located relative to the tool racks and/or the base of the robotic arm, and where the working end must be positioned in order to connect to a particular end-effector on the tool rack.
The teaching process is typically performed by an operator who, by hand or by local controls, moves the working end of the robotic arm toward the tool rack and into the appropriate position for attaching to the desired end-effector. Once the working end is properly connected to the end-effector, the resulting spatial pose of the robotic arm relative to its base may be stored in memory. By programming the spatial poses for each individual tool location in the rack, such as in the form of presets, the robotic arm may be able to simply recall any one of the spatial poses and autonomously replace or attach to an end-effector located at that tool location. During the teaching process, however, the operator must properly align the end-effector to the robotic arm, not only using linear motions but also rotational motions, within six degrees of freedom, which can be difficult due to the limited visibility of universal or quick-change connectors. Although some conventional connector plates provide alignment pins to aid the alignment process to some extent, there is still much room for improvement in the teaching process.
Accordingly, there is a need for improved techniques for aligning a robotic arm to a stationary end-effector, which provide simple and yet effective ways to reduce unknowns during the alignment process.